The invention relates to a drive shaft structure for the minute and hour gears of a timepiece, especially a wristwatch which includes a Belleville spring disposed between two gears.
A wristwatch including such drive shaft structure is well-known in the prior art.
Especially quality watches usually have such drive shaft structures with Belleville springs between the two radial gears in order to take up any play between the two gears and the associated pinion gears. The two radial faces are usually formed by the side surface of the gear as far as the hour gear is concerned and by the side surface of a collar formed on the pinion gear or by a washer disposed on the shaft adjacent the pinion gear. Modern manufacturing of such watch operating mechanisms requires not only miniaturization of the various parts of such mechanisms but these parts should also be adapted to be manufactured by robots and assembled automatically. For miniaturization a collar of relatively large diameter to be provided on the pinion gear is objectionable so that generally the mounting of a washer onto the minute gear shaft is preferred. The sliding of such a washer onto the ger shaft however requires an additional assembly step during manufacturing of the watch and therefore increases assembly time and increases the manufacturing cost.
It is therefore the principal object of the present invention to provide such a watch hand drive arrangement which is small in volume for the required miniaturization and which permits omission of the washer and, of course, of the step of assembling such washer.